Modelling the human brain by modelling its evolutionary emergence

Frans van der Walle fw.novoware at wxs.nl
Tue Feb 26 05:04:34 EST 2002


mat <mats_trash at hotmail.com> wrote:in
43525ce3.0202250446.1eff100f at posting.google.com...
> It is a little clearer now and many of the problems I raised are
> dissipated becuase in fact your project is clearly NOT MODELLING THE
> EVOUTION OF THE BRAIN.  If you start out with 'neuronal assemblies'
> then what you are in fact doing is more akin to modelling the
> embryonic and post-natal development of the brain.  Nothing to do with
> evolution.  This is not to denegrate the merits of the project, but to
> just be explicit about what you are doing. What your project may do is
> highlight some of the developmental mechanisms by which the immature
> brain responds to its environment.  But again this is not evolution.
>
> A few points concerning your 'new' project though - Similarly with the
> problems I raised to the 'evolutionary project', the insight you will
> gain from this experiment is very much more limited than I think you
> appreciate.  All that you will be able to do is perhaps abstract some
> general rules as to morphogenesis of the CNS, but because you do not
> start the modelling from a system that is as richly detailed as the
> 'real' developing brain, you have noe way to ensure that the
> development you observe is in any way a reflection of the real brain.
> Though it may perform in elementary functional testing in a similar
> manner to the brain, that is no guarantee that 'whats inside the box'
> is the same.  Electronic cars and those with internal combustion
> engines can both travel at 30mph, but that doesn't mean they are the
> same underneath the bonnet.
>
> Also, from where do you know that cortical columns are 'simple
> hopfield networks'?  I think it very unlikely that all cells within
> the column are connected to all others.  Many will be connected more
> thna once, some not at all.  Again this bears out what I say above -
> where you start from has a huge influence on where you end up, and the
> conclusions you can draw from the project.
>
> Lastly, what are your 'analyses'?  What data have you looked at in
> coming up with your project?  Be explicit - not just the thoughts of
> some people - actual data about cortical architechtonics.
*******************************

Thank you for your comments. Your remarks show the difficulty with this news
group
approach (this is the first time I participate). Let me show this by one
example. My modelling
of cortical columns of 0.75 mm diameter (not the much smaller ones with some
100 neurons,
often mentioned in the publications by Vernon B Mountcastle) is just one of
the many
outcomes of a much broader analysis of the six layered structure of the
neocortex regarding
its functional interpretation. It resulted in a number of modelling
conclusions:

The first one is that layer I (upper layer) is in fact part of the (several)
million fiber bundle of
the feed forward / backward network that 'spans' the entire brain and spinal
cord (i.e. the
CNS) and that connects some 81 nodal points in the encephalon part of the
brain (= hidden
layers in network terminology), of which some 55% are located in the
functional centers of
that neocortex. These fiber bundles are represented, among others, by the
various fasciculi of
the cortex. The other nodal points are represented by the various nuclei.
This modelling
statement is supported by the fact that layer I emerged first in evolution
some 400 million
years ago with early vertebrata. The other layers emerged later in evolution
and represent
therefore more advanced developments of the hidden layers / nodal points in
that feed
forward / backward network, as represented by cortical functional centers
and nuclei. The
experimental results of Singer and others lead then to the postulate that
information transfer
along this feed forward / backward network takes place in 'blocks' at 200
msec (serial
transfer in lower brain regions) or at 25 msec (parallel transfer in higher
brain regions)
intervals. Justification for this 25/200 msec ‘chopping procedure' can be
found in various
publications referring to experiments in several mammal lines; its
evolutionary emergence
can be traced by publications like that of Winson (see my literature list).
It is a complex
modelling operation, with many parallel observations, that can not be
described adequately in
these short news group discussions. I got already a remark: 'Shorten your
posts!'.

The second conclusion refers to the above mentioned cortical columns. This
part of the
modelling is the result of an extensive interpretation effort, using a large
number of
experimental data from many sources. It leads to the conclusion that
Hopfield type networks
could exist within two neighbouring cortex layers within a cortical column.
This conclusion is
supported by the evolutionary analyses that showed that it is very probable
that such
structures would have emerged. Whether or not such a modelling is correct is
solely
determined by the outcome of the question:
     'Are the characteristics of the model reasonably isomorph with the
functionality of the
     'real thing', i.e. Homo?'
That is one of the reasons that the publication 'Biography of Man' comprises
also some 600
pages dedicated to an application of the modelling effort to fields like:
ethics, psychology,
psychiatry, religion, culture, politics, law and crime / terrorism.

Evolutionary analyses played further a large role in concluding that the
information handling
structure, and its implementational counterpart, can be characterized by a
highly recursive
(fractal) structure, enabling to reduce the brain's (or better: CNS's)
immense complexity to
some hierarchical structure of in itself simple elements. One can not come
to this conclusion
by studying only the CNS as it is now.

This is the first time I participate in a news group discussion and I
certainly appreciate your
comments but I fear that this is not the right medium for my purpose. I
appear not to be able
in provoke fellow scientists to take the (large) trouble by reading /
studying the essential part
of the modelling effort that is present in the first 400 pages of ‘Biography
of Man' (see my
preceding communication of 23-02-2002). That will be the only way to arrive
at a real
discussion on the merits and validity of the modelling approach.

I look forward to your comments.
Frans van der Walle





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